Traffic related air pollution includes diesel engine exhaust derived polycyclic aromatic hydrocarbons (PAH) that have been linked with asthma. Inhaled B{2}-adrenergic agonists engage membrane bound B{2}-adrenergic receptors (B{2}AR) on airway epithelial and smooth muscle cells to cause airway dilation. Preliminary data produced for this application indicate that a diesel exhaust derived mixture of PAHs (DDPAH) impede B{2}AR mediated airway dilation in normal mice and mice with ovalbumin-induced allergic asthma. In vitro studies indicate that DDPAH attenuates B{2}AR function in airway epithelial and smooth muscle cells. These new findings caused us to hypothesize that traffic-related PAH may impede B{2}AR mediated airway relaxation in asthmatics. This hypothesis suggests a new paradigm where air pollutants not only worsen childhood asthma but diminish responsiveness to standard therapy. To test this hypothesis we are proposing 3 aims regarding the effect of traffic-related PAH (TR-PAH) on airway B{2}AR function. Aim 1: Determine if traffic-related PAHs affect B{2}AR expression and function in airway epithelial cells in vitro. Primary mouse tracheal epithelial (MTE) and human airway epithelial cells will be treated with environmentally relevant concentrations of a DDPAH or a mixture of PAH that matches exposures of children in the CCCEH cohort described in project 1 (CCCEH-PAH) prior to assessment of the B{2}AR and its signal transduction pathway. Aim 2: Ascertain if traffic-related PAHs affect B{2}AR function in airway smooth muscle cells in vitro. Human airway smooth muscles cells will be exposed to environmentally relevant concentrations of DDPAH or CCCEH-PAH prior to assessment of the B{2}AR and its signal transduction pathway. Aim 3: Determine if TR-PAHs alter airway B{2}AR function following in utero and early life exposures? The experiments in this aim will test if prolonged exposure to DDPAH or CCCEH-PAH alters B{2}AR -mediated reductions in airways reactivity in young mice. These experiments will utilize mouse models of in utero and early-life exposure that model the windows of asthma susceptibility being investigated in projects 1, 2, and 3. These experiments will be conducted in normal mice, mice with allergic asthma (ovalbumin immunization and rechallenge), mice with targeted deletions of the B{2}AR, and mice with interruption of epithelial cell B{2}AR function. The focused studies within these aims incorporate environmentally relevant PAH exposures, molecular tools, clinically relevant cell lines, genetically engineered mice, and gene transfer to generate models that will allow us address a novel hypothesis regarding the interaction of airborne pollutants and asthma. These experiments complement the studies outlined throughout this DISCOVER project to provide new insights into how common air pollutants affect children's lung health.